Wound mark allowed to become red (7)
I believe the answer is:
scarlet
'red' is the definition.
(I know that red can be written as scarlet)
'wound mark allowed to' is the wordplay.
'wound mark' becomes 'scar' (I've seen this before).
'allowed to' becomes 'let' (to let something happen is to allow it).
'scar'+'let'='SCARLET'
'become' acts as a link.
(Other definitions for scarlet that I've seen before include "Red colour of clarets" , "bloody?" , "Fallen" , "Vivid red" , "Bright red of clarets" .)